III-nitride crystals such as AlxGa1-xN (0<x≦1, likewise hereinafter) single crystals are extraordinarily useful as materials for building semiconductor devices such as light-emitting diodes, electronic devices, and semiconductor sensors.
Examples that have been proposed of how to manufacture such III-nitride single crystals include vapor-phase techniques, particularly among which sublimation has been singled out from the perspective of obtaining crystals of satisfactory crystallinity with a narrow full-width at half-maximum for the X-ray diffraction peak. (Cf., for example, the specifications for U.S. Pat. No. 5,858,086 (Patent Document 1), U.S. Pat. No. 6,296,956 (Patent Document 2), and U.S. Pat. No. 6,001,748 (Patent Document 3).)
However, with attempts to manufacture by sublimation a bulk III-nitride single crystal—for example (repeated similarly hereinafter), 2 inches (approximately 5.08 cm) in diameter×2 mm or more in thickness—leading, due principally to the fact that no high-quality crystals ideal for undersubstrates exist, to problems of crystal growth being nonuniform and of increased dislocation density, crystallinity degradation, and incidents of polycrystallization, methods of stably growing AlxGa1-xN single crystal of practicable size, and of low dislocation density and favorable crystallinity have yet to be proposed.    Patent Document 1: U.S. Pat. No. 5,858,086 specification    Patent Document 2: U.S. Pat. No. 6,296,956 specification    Patent Document 3: U.S. Pat. No. 6,001,748 specification